1. Field of the Invention:
This invention relates to materials which are useful in extending the pot life of propellants with hydroxy terminated polymeric binders, cured with multiisocyanate curatives.
2. Description of the Prior Art:
Hydroxy terminated polymeric binders are well known and widely used in solid rocket propellants. One example is hydroxy terminated polybutadiene (HTPB). It and other hydroxy terminated binders are normally cured by means of diisocyanates and other multi-isocyanates. When an isocyanate curing agent is added, the viscosity of the HTPB binder begins to increase immediately. Once an isocyanate curing agent is added, the time remaining in which the viscosity of HTPB propellant or the like is low enough so that one can work with it is relatively short. Consequently, during a propellant mix cycle, the curative is generally added near the end of the cycle. This usually leaves enough time for the person doing the mixing to finish working the propellant into the motor, quality control carton or whatever else it is to be in before it becomes unworkable. However, should the propellant contain a transition metal compound (such as, for example, an iron compound as a burning rate accelerator) as propellants often do, the working time, i.e., pot life, of the propellant sometimes becomes unworkably short after the curative is added. Many transition metal compounds, including iron compounds, act as catalysts in accelerating the cure reaction, reducing the working time of the propellant.